It is proposed to study the role of cytochrome P450 enyzmes of the adrenal cortex in the control of glucocorticoid and mineralocorticoid biosynthesis. The method by which cholesterol side chain cleavage is activated by ACTH will be examined in several projects: (1) in which the circadian rhythm of corticosterone will be used as a means of examining low and high activity of the glucocorticoid pathway, (2) in which we will attempt to demonstrate that ACTH stimulates the phosphorylation of a specific factor involved in the activation of cholesterol side chain cleavage, and (3) in which we will examine the activation of cytochrome P450scc in a cortisol secretor, the guinea pig. In a related project, the control of aldosterone biosynthesis will be examined and the influence of several agents on the cytochrome P450scc and cytochrome P450-18 of the zona glomerulosa studied. The techniques to be used in these studies are those developed by us for examining the interactions of substrates such as cholesterol and corticosterone with the cytochrome P450 systems of the adrenal cortex. A combination of light absorption spectrophotometry and EPR spectroscopy will be used. NEW DIRECTION: This supplemental application has been necessitated by our finding that another factor from the pituitary, other than ACTH, may be involved in the response of the adrenal cortex to stress. Experiments are described which will evaluate peptides derived from the "16K" portion (N terminal) of pro-opiocortin as to their existence in blood and their role in the control of corticosteroidogenesis.